Currently, the importance of the vomeronasal system to the mating behavior of male hamsters is being tested. In agreement with the results of Winans and Powers, we are finding that sectioning the vomeronasal nerve results in severe disruption of copulatory behavior in 30% to 40% of males. However, in contrast to their findings, our hamsters have been showing eventual recovery from the lesion. In an extension of their work we have determined that the deficit produced by vomeronasal damage is essentially the same in sexually naive and sexually experienced hamsters.